Fluoride therapy in postmenopausal osteopenic women: Effect on vertebral and femoral bone density and prediction of bone response

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Abstract
Fifty-two postmenopausal women (mean age 60±5 years) with low BMD (<-2SD of young adult values) but who had not experienced previous crush fracture were treated with 50 mg of sodium fluoride (NaF), 1 g of calcium and 400 IU of vitamin D2 per day for 2 years. Repeated vertebral and femoral BMD measurements were made and compared with those of a control group consisting of 16 untreated women. Serum alkaline phosphatase and osteocalcin, blood and urinary fluoride levels were measured regularly to determine their predictive value on bone response. 18 of 52 (35%) of the treated patients experienced side effects (29% gastric, 4% lower extremity pain syndrome) but only in 6 cases (12%) was it necessary to discontinue treatment. In neither of the two groups was any fracture recorded (vertebral or otherwise). Among the 43 women who were treated for at least 2 years, 21 (49%) were considered to have responded (i.e., with an increase of vertebral BMD>0.043 g/cm2). There was a mean linear increase in BMD in this group of 0.0041 g/cm2 per month (i.e., 5.5% per year). On the other hand in the non-responder group and in the control group, vertebral BMD either remained stable or decreased. However no difference was detected between the two groups (treated and controls) at the femoral site after 2 years; both groups showed a significant decrease in BMD. The responders had a lower initial osteocalcin level and treatment led to a relatively greater increase in osteocalcin. Moreover basal and post-treatment levels of alkaline phosphatase and blood and urinary fluoride did not differ significantly between the two groups. An increase in serum osteocalcin of more than 50% had the best predictive value for bone response. However, this increase did not allow bone response to be predicted any earlier than direct bone measurement; the majority of responses being identified after 12–18 months of therapy. This study shows the ability of NaF to increase vertebral BMD without altering femoral density in women with low vertebral BMD but no fracture. However it is impossible to predict to what extent this increase in BMD will modify the ultimate risk of fractures.